Stumbling towards a memory

A few months ago, I stumbled upon a manga. It wasn't very popular (as far as I know), flashy or inventive. It was more on the reflective side. But, I kept reading it, because one of the characters reminded me of someone I know. Last week, I stumbled on the anime version of that same manga. The feel didn't differ much from the book. I again stayed because of the resemblance to my friend, but then the ending song started playing. The melody was simple and melancholy, with lyrics that I could understand relatively well, even without the translations. And it was those lyrics that stopped me in my tracks...because it was a pretty good reflection of why I kept reading and watching...hmmm...懐かしい、な。。。